1. Field of the Invention
The present invention relates to an ink pot device for the printing machine in the offset printing system, more particularly to an improvement of the ink pot device for the offset printing machine, in which the supply rate of ink is decreased or increased by driving a plurality of ink keys that are arranged in due order, individually forwardly or backwardly.
2. Prior Art
In the prior art, this type of ink pot device requires such skills to move the ink keys for controlling inking rates that the device can be operated only by those skilled in the art for long time. However, other devices in the printing system are operable without requiring such a degree of skills. Therefore, it is demanded to develop an ink pot device for the offset printing machine, in which even an unskilled operator can simply and easily adjust the strokes of the ink keys.
When inking rates are adjusted manually by moving the ink key, it is preferred that the operation can simply and precisely be conducted in higher work efficiency.
Another aspect of the present invention relates to such an ink pot device for the printing machine that inking rates for printing are adjusted by controlling a stepping motor for adjusting the ink keys through a simple electrical control.
Such a type of ink pot device based on this electrical control known in the prior art is shown in FIG. 3 Electrical circuit diagram in which an ink key adjusting servomotor is provided for each ink key and located according to the ink supply rate data sent from the control panel, while also being controlled by the feedback data sent from the potentiometer for setting the ink keys.
Consequently, a servomotor and a potentiometer must be used for each ink key in the ink key adjusting device where the number of ink keys, servomotors or potentiometers in use is 20-40 for the 1 unit (1 color) system, although depending on the size of printing material, while the number being quadruplicated or hexaplicated for 4-color or 6-color printing. In addition, an expensive servoamplifier is required in the control panel. Therefore, the ink supply control system was much expensive in fact. Furthermore, each servomotor and potentiometer are connected through 2-stage gears, requiring many adjusting positions and large dimensions. Moreover, the servomotor is a DC machine having limited life in the brush as well known in the art. Accordingly, such a system known in the prior art has some disadvantages in view of maintenance, control and reliability for a long time use. Another aspect of the present invention relates to an improved mechanism for controlling the opening of the ink outlet port in the ink pot device for the printing machine.
A system of the ink outlet port opening adjusting mechanism for this type of ink pot device, as known in the prior art, is shown in FIG. 13. According to this system, the upper and lower limits of the adjusting mechanism are obtained by applying a counter force in the direction resistive to the axial movement of driving force transmission gear 57, onto transmission gear 57 by means of a butt type stopper protrusion 63. In consequence, an inner screw and threads in a screw bolt often come in so-called gouged state in driving force transmission gear 57. When shuttling motion of the driving force transmission gear takes place after butting with stopper protrusion 63, gouging causes sluggishness and non-smooth operation. In addition, the driving force transmission gear becomes unstable while slidedly dislocating stop position when butting with stopper protrusions 63. These disadvantages were associated with this type of ink pot device known in the prior art.